The cell cycle and cell division Cell cycle interphase prophase mataphase anaphase telophase DNA content/ arbitary units Interphase division Cytokinesis A B C D Mitosis The significance of mitosis is that it produces cells which are genetically identical to the parent cell, giving genetic stability. This is cell division for: • growth • epairing damaged cells • replacement of old, worn out cells • sexual reproduction. The cell cycle is controlled by genes. If the genes that regulate the cell cycle are damaged, uncontrolled mitosis can occur. This rapid replication of cells can form tumours, leading to a disease called cancer. These genes that cause cancer are called oncogenes. IPMAT-can be used to remember the order of the phases in mitosis: Cytokinesis Where telophase is the division of the nucleus, cytokinesis is the division of the cytoplasm to create the 2 new genetically identical cells. In plant cells there are some differences: • There are no centrioles in plant cells. • In cytokinesis, a cell plate (droplets of cell wall material) develops from the centre out instead of cleavage from the outside in as in animal cells. Prophase Metaphase Anaphase Telophase • Chromosomes condense and become visible • Centrioles move to opposite sides of cell • Spindle forms from microtubules • Nuclear envelope disintegrates. • Centromeres of chromosomes attach to spindle and line up on the equator. • Spindle fibres shorten • Centromere separates and individual chromatids are pulled to the pole’s centromere first. • Spindle breaks down • Chromosomes uncoil • Nuclear envelope reforms. The cell cycle is a natural cycle of events that occur in the life of a cell. During most of the cell cycle the cell remains in a phase called interphase. Interphase is a time of high metabolic activity for the cell: During section A of the graph below, the following occur: Replication organelles like mitochondria and chloroplasts which have their own DNA. Making new organelles. Synthesis of ATP. Synthesis of proteins. Increase in cell size. During section B: Replication of DNA.